The 3rd Generation Partnership Project (referred to as 3GPP) Evolved Packet System (referred to as EPS) is composed of Evolved Universal Terrestrial Radio Access Network (referred to as E-UTRAN), Mobility Management Entity (referred to as MME), Serving Gateway (S-GW), Packet Data Network Gateway (referred to as P-GW or PDN GW), Home Subscriber Server (referred to as HSS), 3GPP Authentication, Authorization and Accounting (referred to as AAA) server, Policy and Charging Rules Function (referred to as PCRF) entity and other support nodes.
FIG. 1 is a structural diagram of an EPS system in the related art, as shown in FIG. 1, the MME is responsible for control plane related work such as mobility management and non-access stratum signaling processing; the S-GW is an access gateway device connected with the E-UTRAN, forwarding data between the E-UTRAN and the P-GW, and it is responsible for buffering the paging waiting data; the P-GW is a border gateway between the EPS and the packet data network (referred to as PDN), and it is responsible for the PDN access, forwarding data between the EPS and the PDN, and other functions. In the 3GPP, the corresponding PDN network can be found out through the Access Point Name (referred to as APN). Usually, a connection from a User Equipment (referred to as UE) to the PDN network is called an IP Connectivity Access Network (referred to as IP-CAN) session.
One important feature of the mobile network is to maintain the service continuity in a process that the UE consistently moves. In the EPS system, the continuity is ensured by the mobility management functions, mainly including handover and tracking area update, of the system handover. Said mobility management serves to ensure the continuity of the UE services, to ensure that the UE is always reachable in the view of the outside when the UE moves in the network, so that the UE and the peer end communicating with the UE do not have a perception in the IP level that the UE's location changes. In brief, the UE has a valid IP address unchanged in the moving process. In the process of mobility management, the UE may change the currently connected S-GW, and this scenario will be described in the following.
As shown in FIG. 2a, the S-GW to which the UE is currently connected changes, and the source eNodeB and the target eNodeB are connected to different S-GWs. When the UE moves from the service area of source S-GW to the service area of target S-GW, the network (or the UE itself) is triggered to change the currently connected S-GW for the UE. Before the change (on the left side in FIG. 2a), the uplink and downlink data transmission path of UE is: UE<->source S-GW<->P-GW<->PDN network; after the change (on the right side in FIG. 2a), the uplink and downlink data transmission path of UE is: UE<->Target S-GW<->P-GW<->PDN network. It can be seen that before and after the S-GW changes, the uplink and downlink data of UE always pass through the same P-GW, and the P-GW remains the same, and said P-GW is referred to an Anchor Point of the UE.
No matter how the UE moves, its anchor point will not change, that is, the P-GW to which the UE is attached does not change. Such unchanged anchor point will trigger a series of problems. For example, it might lead to the circuitous routing problem widely recognized in the industry, that is: in a process of one connection as well as a process of the UE using service, the location of UE might change, and when the current location of UE is leaving away from its anchor point, the data flow that the UE interacts with the outside also needs to be forwarded by its anchor point, particularly when the current location of UE is relatively close to the service source that the UE accesses, the circuitous routing problem becomes more apparent (FIG. 2b).
The circuitous routing brings problems in the following aspects:
(One) wasting the transmission bearer resources of operators, which is not conducive to cost savings;
(Two) increasing the delay of transmitting and receiving IP packets between the UE and its communicating peer end, which is not conducive to improving the user's service experience;
(Three) increasing the likelihood of network congestion when the UE's IP packets are transmitted over the network, resulting in that the UE services, for example real-time services such as voice and video, are hindered or even impossible to be implemented.